NATO Secretary-General Jens Stoltenberg met with U.S. Secretary of State Antony Blinken and other NATO foreign ministers in Brussels on Friday morning to discuss the response to the ongoing Russian invasion of Ukraine.

During a press conference prior to the meeting at NATO headquarters, Blinken and Stoltenberg condemned Russia's attacks on civilians in Ukraine and expressed concern over the reports of Russian shelling at Ukraine's largest nuclear power plant.

"This just demonstrates the recklessness of this war and the importance of ending it, and the importance of Russia withdrawing all its troops and engage in good faith in diplomatic efforts," Stoltenberg told reporters. "We provide support to Ukraine. At the same time, NATO is not part of the conflict. NATO is a defensive alliance, we don't seek war conflict with Russia."

Blinken emphasized that NATO and the United States "seek no conflict."

"But if conflict comes to us, we're ready for it," he added. "And we will defend every inch of NATO territory."

The head of the United Nations nuclear watchdog said Friday that no radioactive material was released at Ukraine's largest nuclear power plant amid shelling from Russian forces overnight.

The shelling sparked a fire in a training building at the Zaporizhzhia nuclear power plant, the largest in Europe, in the eastern Ukrainian city of Enerhodar. The blaze has since been extinguished, according to Ukraine's State Emergency Service.

Two security employees at the plant were injured during the incident, according to International Atomic Energy Agency (IAEA) Director-General Rafael Mariano Grossi.

"The safety systems at the six reactors were not effected," Grossi said at a press conference in Vienna on Friday morning. "No radioactive material was released."

"We are following the situation very, very closely," he added.

-ABC News' Joe Simonetti

A fire at the Zaporizhzhya nuclear power plant in the eastern Ukrainian city of Enerhodar was extinguished Friday, according to Ukraine’s State Emergency Service.

The fire occurred in a training building at the site after shelling from Russian forces. There were no victims, the emergency service said.

The Zaporizhzhia nuclear power plant is the largest in Europe.

Meanwhile, Energodar Mayor Dmytro Orlov told reporters Friday morning that the city is now under the control of Russian forces and fighting near the Zaporizhzhya nuclear power plant has stopped. It's the second Ukrainian nuclear facility to fall under Russian control since the invasion began Feb. 24. Last week, Russian forces seized the Chernobyl nuclear power plant, where the world's worst nuclear accident took place in 1986, and the surrounding exclusion zone, which includes the ghost city of Pripyat.

Ukraine's national nuclear regulator has said that the Zaporizhzhia nuclear power plant's employees are being permitted to work as normal, safety systems are currently functioning and there was no reported change in radiation levels at the site.

-ABC News’ Brian Hartman and Patrick Reevell

The International Atomic Energy Agency (IAEA) has appealed for a halt of the use of force at Ukraine's largest nuclear power plant and warned of "severe danger if any reactors were hit."

The United Nations nuclear watchdog said in a statement early Friday that it was informed by Ukraine that the Zaporizhzhia nuclear power plant, the largest in Europe, had been shelled overnight in the eastern city of Enerhodar. IAEA Director-General Rafael Mariano Grossi "immediately" spoke with Ukrainian Prime Minister Denys Shmyhal as well as the country’s national nuclear regulator and operator about the "serious situation." Grossi is expected to hold a press conference later Friday.

According to IAEA, the Ukrainian regulatory authority said a fire at the site had not affected "essential" equipment and plant personnel were taking mitigatory actions, and that there was no reported change in radiation levels at the plant.

Ukraine's State Emergency Service said the blaze, which occurred in a training building after shelling from Russian forces, was extinguished Friday morning.

The IAEA said it is putting its Incident and Emergency Center (IEC) in "full response mode" due to the situation at the Zaporizhzhia nuclear power plant. The agency continues to closely monitor developments at the facility and remains in constant contact with Ukraine.

The Russian forces charging toward Kyiv haven't made progress in the last day as they face Ukrainian resistance and low food and gas supply, a senior U.S. defense official told reporters Tuesday.

However, it could be a deliberate pause, the official said. "Part of the stall could be ... as a result of their own self-determined sort of pause in operations -- that they are possibly regrouping, rethinking, reevaluating," the official said.

The U.S. believes Russian forces "have committed now more than 80% of what was their pre-staged combat power," the official added.

The official said some Russian soldiers weren't told they were going into combat. The official said "not all of them were apparently fully trained and prepared."

The strong Ukrainian resistance has also hurt morale, according to the official.

Russia has now launched more than 400 missiles on Ukraine, the official said. The U.S. believes Russia has launchers that could be used for thermobaric weapons, but cannot confirm their use, the official said.

Russian forces are making the most progress in the south. Russians are attacking Kherson in south Ukraine, which "appears very much to be contested city at this point," the official said.

Russians are also approaching Mariupol in southeastern Ukraine, and while they haven't yet entered the city, "they are close enough now that they could attack Mariupol with long range fires," the official said.

Two towns on the path to Mariupol are believed to be occupied by the Russians, according to the official.

The U.S. believes the Russians hope to move north out of Mariupol up to the heavily-contested city of Kharkiv. The official said they believe Russian forces are trying to encircle Kharkiv.

The U.S. official noted that they've seen "certain risk-averse behavior by the Russian military" over the last week.

"Take the amphibious assault, for instance. They put those troops ashore a good 70 kilometers away from Mariupol because they knew Mariupol was going to be defended and they could put them ashore in an uncontested environment. And they still haven't reached Mariupol," the official said.

"They are not necessarily willing to take high risks with their own aircraft and their own pilots," the official said.

"And of course we're seeing that on the ground -- the fairly slow and steady progress that they have made, and you guys are seeing it for yourselves on the ground where ... units are surrendering, sometimes without a fight."

-ABC News' Matt Seyler